Brake disk and method of making same

ABSTRACT

A brake disk or drum has at least one working surface which opposes a braking member such as a brake pad or shoe. A plurality of spaced, raised island formations are provided across the working surface, with channels extending between the island formations. Each raised island formation has an outer surface which contacts a brake pad or brake shoe during braking.

RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.12/195,994, filed Aug. 21, 2008, which claims the benefit of U.S.provisional patent application No. 60/957,422, filed Aug. 22, 2007 andU.S. provisional patent application No. 60/971,879, filed Sep. 12, 2007,each of which are incorporated herein by reference in its entirety.

BACKGROUND 1. Field of the Invention

The present invention pertains generally to brake disks (also referredto as rotors) and drums made of cast iron, carbon steel, stainless steelor a ceramic/metal composite material with a functionally engineeredfriction surface, and to methods of making such brake disks.

2. Related Art

During braking, hydraulic energy is used to press the vehicle's brakepads against the rotating brake disk. The friction resulting from themoving contact between brake pad and brake disk slows the rotation ofthe brake disk and decreases the speed of the vehicle. This frictionalcontact generates heat and causes the contact surfaces on the brake padand brake disk to wear unevenly. Excessive wear can cause the brake diskto become thin and weak resulting in warpage and brake fade. In somecases, the thinning of the brake disk becomes so severe that the brakedisk is no longer able to support the stresses and heat generated duringbraking. The result is typically a warped brake disk that can causeundesirable brake chattering and an unsafe brake system.

A factor that can be considered when designing brake rotors isaesthetics. Modern motorcycles have rather large diameter brake disksthat are plainly visible, especially the front disk(s). Because of thisvisibility, the color and surface appearance of a brake disk can add toor detract from the overall look of the motorcycle. These considerationscan affect a purchaser's decision when buying a new motorcycle and alsowhen retrofitting a motorcycle with a new brake system.

In view of the foregoing, there are a number of reasons why it isimportant for a brake disk (also sometimes referred to as a brake rotor)to dissipate heat while at the same time to be wear and corrosionresistant. First, the ability of the brake disk to dissipate heat helpseliminate the possibility of brake fade, wear and subsequent warpage.This, in turn, would potentially lead to a longer service life for thebrake rotor. A longer service life translates into reduced maintenanceand the associated costs. Additionally, the ability of the brake disk todissipate heat faster would result in less brake fade which would add tothe safety aspects of the overall braking system. A final consideration,which is especially important for brake disks used on motorcycles (orwherever the brake disk is exposed to general view), is the appearanceof the brake disk.

SUMMARY

Embodiments described herein provide coated brake disks that have raisedisland formations integrated into one or both of the parallel workingsurfaces of the disk with channels extending between the islandformations that improve the dissipation of the heat generated during thebraking process, and methods for making such brake disks with integralisland formations. The outer surfaces of the island formations may begenerally flat and act as the friction surfaces which engage theopposing brake pad on braking. In one embodiment, a brake disk isdisk-shaped having a central hole (or in some cases multiple holes) toallow the brake disk to be positioned over a hub and attached to a motorvehicle. The brake disk is further formed with a pair of annularsurfaces that extend from the central hole to the periphery of the brakedisk, and each annular surface has a plurality of raised islandformations or lands at spaced intervals across the surface, withchannels defined in the spaces between adjacent island formations. Theisland formations are provided for contact with the brake pads duringbraking and constitute the wear or working surfaces for the brake disk.Island formations can be provided in any shape or size as long as theyprovide a sufficient friction or working surface area based on brakingperformance criteria. The island formations can also be designed to beornamental in appearance to enhance the aesthetic appearance of exposedportions of the disk surfaces.

In accordance with some embodiments, the brake disk or rotor can be madeof cast iron, stainless steel or a light weight ceramic material orceramic composite material, or combinations thereof. One or both workingsurfaces include a plurality of spaced island formations on contactsurfaces. The air flow channels between adjacent island formations allowfor improved air flow over the working surface in order to improvedissipation of the heat generated during the braking process. The brakedisks with the island formations are coated with or include a coatingmaterial that is wear and corrosion resistant. The coating material mayhave an aesthetically pleasing appearance and may be deposited onportions of the brake disk that are visible when the brake disk isinstalled on the vehicle. In one embodiment, the coating is deposited onthe entire brake disk. Alternatively, the coating may be deposited onlyon the island formations. Coating materials of different colors orproducing surface textures or appearances may be provided on differentregions of the disk surfaces, for example on the island formations andchannels between the island formations, for enhancing the appearance ofthe disk.

The specific size, shape, directional alignment, depth of air flowchannels and the surface finish of the channels can be introduced to thebrake disk surface by utilizing a variety of methods. The islandformations may be imparted to the brake surfaces by various machining orforming techniques, including bead blasting, grinding, acid etching,laser etching, roll forming, embossing, stamping, honing, lapped,polished, blanched, milled, profiled or any other machined surfacetreatment or surface geometry modification and any combination(s)thereof.

In one embodiment, a surface finish or texture is produced on the entirearea of the annular surface or on the island formations alone, prior toapplication of any coating layers. The desired surface texture may beproduced by blasting the brake disk surface with a continuous stream ofparticles (commonly referred to as bead blasting) which are typicallyharder than the brake disk surface. These particles can be round inshape or very irregular in shape. The various particle shapes impart adifferent surface finish or surface geography to the brake disk. Forexample, with round particles (of various sizes) and appropriateparticle energy (air pressure or hydro pressure) a surface texture thatmicroscopically resembles low soft rolling hills can be achieved. Withirregular (crystalline) shaped particles, a very coarse surface geometry(very rugged/jagged peaks and valleys) can be imparted to the brake disksurface. Other methods such as a sanded or a ground surface finish canbe used to give a different appearance when coated with the wear andcorrosion resistant coating. When the sanded or ground surface finish isdone in a cross-hatched configuration and then coated with the wear andcorrosion resistant coating, the coated brake disk can be made to lookas though it has a woven appearance such as is found in components madefrom carbon fiber. In general, there are a multitude of surface finishtechniques that can be utilized to impart a specific surface texture orgeometry into the brake disk.

In one embodiment, a coating is deposited on all or part of the oppositeannular surfaces of the brake disk. The coating may be applied only tothe island formations which contact the brake pads, or may extend overthe entire surface including the island formations and the channelsbetween the island formations. In one embodiment, the coating includes afirst layer of a material having either an amorphous structure (i.e. anon-crystalline structure), a crystalline structure, or a mixture ofamorphous and crystalline structure materials. In a particularembodiment, the material of the first layer is a metal such as titanium,chromium, zirconium, aluminum, hafnium or an alloy thereof. The firstlayer is applied directly on the brake disk. The coating furtherincludes a second layer that overlays and contacts the first layer. Inone embodiment, the second layer includes one or more metal nitrides,metal borides, metal carbides and metal oxides. The second layer mayinclude one or more nitrides, borides, carbides or oxides of the metalused in the first layer. For example, for a coating having titanium asthe first layer, the second layer can be titanium nitride (TiN). Note;the abbreviations (e.g. TiN) are used herein as a shorthand rather thanan exact chemical label, and do not suggest that the stoichiometry ofthe indicated compound must be exactly as stated in the abbreviation.

In one embodiment, after machining a brake disk with a selectedarrangement of spaced island formations, and applying any desiredsurface finish, coating layers are applied using a physical vapordeposition source such as a cathodic arc source with a controlled gasatmosphere. Other operable techniques such as unbalanced magnetronsputtering or thermal evaporation may also be used. During coatingdeposition, the brake disks are positioned on a fixture and the fixtureis rotated in a planetary movement about a central axis. In greaterdetail, the fixture includes three or more parallel poles that aremounted on a plate and arranged wherein each pole is spaced at an equaldistance from the other poles. A plurality of brake disks can be stackedon each pole, with spacers to separate adjacent disks within each stack.The poles are spaced from each other to allow the brake disks on onepole to overlap the brake disks on an adjacent pole. The spacers preventbrake disks on one pole from contacting the brake disks on an adjacentpole.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of the present invention, both as to its structure andoperation, may be gleaned in part by study of the accompanying drawings,in which like reference numerals refer to like parts, and in which:

FIG. 1 is a perspective view of a motorcycle having a disk brake system;

FIG. 2 is a perspective view of a coated disk brake;

FIG. 3A is an enlarged cross-sectional view of a portion of the coateddisk brake shown in FIG. 2 as seen along line 3-3 in FIG. 2 showing thecoating layers;

FIG. 3B is an enlarged cross-sectional view of the circled area of thecoated surface in FIG. 3A, illustrating one embodiment of a surfacetexture applied to the surface of the disk substrate prior toapplication of the coating layers;

FIG. 4 is a front elevation view of a fixture for supporting the diskbrakes during the coating process;

FIG. 5 is a top plan view of a fixture for supporting the disk brakesduring the coating process;

FIG. 6 is a schematic plan view and control diagram of a depositionapparatus for use in the coating process;

FIG. 7 is a schematic perspective view of a detail of the depositionapparatus of FIG. 5;

FIG. 8 is a schematic cross-sectional view of the cathodic arc source,taken along lines 8-8 of FIG. 7; and

FIG. 9 is a perspective view of a brake rotor surface with fourdifferent surface modifications or “island formations”.

DETAILED DESCRIPTION

Certain embodiments as disclosed herein provide for brake disks withspaced raised surface portions or island formations having anaesthetically pleasing appearance and also providing air flow channelsfor cooling purposes between the adjacent island formations, as well asmethods for making the brake disks.

After reading this description it will become apparent to one skilled inthe art how to implement the invention in various alternativeembodiments and alternative applications. However, although variousembodiments of the present invention are described herein, it isunderstood that these embodiments are presented by way of example only,and not limitation. As such, this detailed description of variousalternative embodiments should not be construed to limit the scope orbreadth of the present invention as set forth in the appended claims.

Referring to FIG. 1, motorcycle 10 is shown that includes a disk brakesystem. As shown, the disk brake system includes a brake disk or rotor12 that is attached to the front wheel 14 of the motorcycle 10 forrotation therewith. Typically two brake disks are attached to the frontwheel of a motorcycle, and one or two brake disks are attached to therear wheel. The brake system further includes a caliper 16 having a pairof brake pads that can be selectively applied against the brake disk 12using hydraulic pressure to slow the rotation of the brake disk 12 andwheel 14. In a typical setup, the hydraulic pressure is provided by themotorcycle operator using a hand lever mounted on the handlebars of themotorcycle 10.

A better appreciation of a brake disk 12 can be obtained with referenceto FIG. 2. As shown, the brake disk 12 is disk-shaped having a centralhole 18 to allow the brake disk 12 to be positioned over the hub of thewheel 14 (shown in FIG. 1). The brake disk 12 is further formed withannular working surfaces 20 a,b (see also FIG. 4) that extend from thecentral hole 18 to the periphery 22 of the brake disk 12. As shown,surface 20 a is parallel with and opposed to surface 20 b on the brakedisk 12. At least a portion of each of the surfaces 20 a,b is designedfor contact with the brake pads during braking, as described in moredetail below. In one embodiment, a surface finish is applied to theannular surfaces prior to coating all or part of each surface with awear and corrosion resistant coating, as described in more detail below.

In one embodiment, the annular surfaces 20 a and 20 b of brake disk 12are provided with a plurality of raised land portions or islandformations with spaced air flow channels between the island formations.Only the island portions contact the brake pads during braking in thisarrangement, and comprise the wear surfaces of the brake disk 12. FIG. 9illustrates some examples of possible land portions or island formationswhich may be provided on the opposite surfaces 20 a and 20 b of disk 12.In FIG. 9, four possible island formations are shown in the fourquadrants of the exposed disc surface 20 a; tear drop shaped formations150, circle or dot shaped formations 152, figure eight shaped formations154, and letter shaped formations 155, with channels or voids 156between the island formations allowing air flow extending between theformations. As seen in three of the quadrants in FIG. 9, the islandformations may be arranged in rows which extend radially from thecentral opening 18 of the disk out to the peripheral edge, with radialair flow channels extending outwardly between each adjacent pair ofrows, in addition to channels which extend between adjacent pairs ofisland formations in each row. The island formations have upper surfaces158 which are at least substantially flat friction surfaces for contactwith the brake pads during braking, and are designed with sufficientsurface areas for braking purposes. The four formations illustrated inFIG. 9 are examples of suitable island formations. Alternative islandformations of different shapes and sizes may be engineered for coolingand wear in order to meet specific performance criteria in addition toproviding an aesthetically pleasing appearance.

In one embodiment, spaced island formations of the shape shown in anyone quadrant of FIG. 9 extend over the entire disk surface.Alternatively, island formations of any desired different shapes andsizes may be provided in patterns over the disk surface. The islandformations can be of any size or shape including but not limited to;letters or names, numbers, logos, trademarks, dashes, other geometricshapes, and the like. The island formations can be designed to beaesthetically pleasing in appearance which is particularly desirablewhen the disk surfaces are externally visible, as is the case with manymotor cycle brake disks (see FIG. 1). The grooves or channels around theisland formations result in a significant reduction in the overallweight of the brake disk which in turn improves the efficiency andperformance of the motor vehicle. Additionally, the channels allow forair flow around the island formations for increased cooling and heatdissipation. The base of each channel may be roughened or modulated toprovide bumps or the like, creating turbulence in air flow along thechannel which may produce enhanced cooling.

Island formations of the desired shape and dimensions may be formed inany suitable manner, for example by appropriate machining or otherforming processes. After machining the desired island formations on oneor both surfaces of the disk, the entire brake disk is coated with awear and corrosion resistant coating 24 which eliminates or greatlyreduces the wear of the island braking surfaces, as generallyillustrated in FIG. 3A. Alternatively, the functional island brakingsurfaces alone may be coated with coating 24. The coating improves theoverall look or aesthetics of the brake disk. In one embodiment, thecoating includes a first layer of a metal, such as a pure titaniummetal, and a second layer that includes a nitride, boride, carbide oroxide of the metal used in the first layer. The coating may be appliedusing a physical vapor deposition source such as a cathodic arc sourcewith a controlled gas atmosphere. The materials used for coating 24 maybe of different colors and may be designed to produce different surfaceappearances, such as a light reflective, shiny appearance, for example,particularly on regions of the surface which are visible when the brakedisk is installed on a vehicle.

In one embodiment, a surface finish may be produced on the surfaces ofthe brake disk substrate, including the island formations, by blastingthe brake disk surface with a continuous stream of particles (commonlyreferred to as bead blasting) which are typically harder than the brakedisk surface. These particles can be round in shape or very irregular inshape. The various particle shapes impart a different surface finish orsurface geography to the brake disk. For example, with round particles(of various sizes) and appropriate particle energy (air pressure orhydro pressure) a surface texture that microscopically resembles lowsoft rolling hills can be achieved. With irregular (crystalline) shapedparticles, a very coarse surface geometry (very rugged/jagged peaks andvalleys) can be imparted to the brake disk surface. Other methods suchas a sanded or a ground surface finish can be used to give a differentappearance when coated with the wear and corrosion resistant coating.When the sanded or ground surface finish is done in a cross-hatchedconfiguration and then coated with the wear and corrosion resistantcoating, the coated brake disk can be made to look as though it has awoven appearance such as is found in components made from carbon fiber.In general, there are a multitude of surface finish techniques that canbe utilized to impart a specific surface texture or geometry into thebrake disk prior to application of a coating 24. In one embodiment,selected surface finishes may be implemented as described in co-pendingU.S. patent application Ser. No. 12/034,590 of Meckel filed on Feb. 20,2008, the entire contents of which are incorporated herein by reference.In alternative embodiments, only the braking surfaces of the islandformations may be treated to produce a surface texture, for example, bymasking the channels between the island formations during bead blastingor other surface treatments.

Coating 24 is shown applied to a brake disk substrate 26 in FIGS. 3A and3B. The brake disk substrate or rotor 26 may be formed of any suitablematerial such as cast iron, stainless steel, light weight metal alloys,ceramic materials, ceramic composite materials, or combinations thereof.The coating 24 may be implemented in one embodiment using the fixtures,techniques and materials as described in co-pending application Ser. No.12/034,590 referenced above, and in co-pending U.S. patent applicationSer. No. 12/034,599 of Meckel filed on Feb. 20, 2008, the entirecontents of which are incorporated herein by reference. The portion ofthe substrate 26 illustrated in FIG. 3A may be part of the top surfaceof an island formation, or part of the channel between adjacent islandformations. As noted above, the entire surface of the disk (islandformations and valleys or channels between island formations) may becoated. In alternative embodiments, the island formations only may becoated.

As further shown in FIG. 3A, the coating 24 includes a first layer 28 ofa material having an amorphous structure (i.e. a non-crystallinestructure) or a crystalline structure. In a particular embodiment, theamorphous or crystalline material is a metal such as titanium, chromium,zirconium, aluminum, hafnium or an alloy thereof. The coating 24 furtherincludes a second layer 30 that overlays and contacts the first layer28. Though the layers are depicted as distinct, in some embodiments, thelayers intermingle or merge such that no distinct boundary existsbetween the layers. The second layer 30 can include one or more binarymetals, for example, one or more metal nitrides, metal borides, metalcarbides and metal oxides. The second layer can include one or morenitrides, borides, carbides or oxides of the metal used in the firstlayer. In some embodiments, the coating may comprise multiple layers ofalternating metal and metal compound materials may be applied in orderto impart specific physical properties to the brake disk or rotor. Insome embodiments of a coating 24, amorphous titanium constitutes thefirst layer 28 and a titanium nitride (TiN, Ti₂N, etc.) constitutes thesecond layer 30. Multiple alternating layers 28, 30 can be configured toform a lattice structure or a super lattice structure. These are thinfilms formed by alternately depositing two different components to formlayered structures. Multilayers become superlatices when the period ofthe different layers is less than 100 Å. With this cooperation ofstructure, a coating 24 having a service life to exceed approximately100,000 vehicle miles or more can be obtained. Note: the abbreviations(e.g. TiN, Ti₂N, etc.) are used herein as a shorthand rather than anexact chemical label, and do not suggest that the stoichiometry of theindicated compound must be exactly as stated in the abbreviation.

FIG. 3B illustrates the optional addition of a surface texture 29 to thesurface of substrate 26 prior to application of the coating layers 28and 30. The surface texture in FIG. 3B is a coarse texture as may beimparted by blasting with irregular shaped particles, as describedabove, and comprises a series of peaks and valleys with angular apicesat each peak and valley. Alternative surface textures may be rounded,cross-hatched, or woven in appearance, as described above. When thetextured surface 29 is subsequently coated with one or more coatinglayers, the resultant, substantially flat surface can exhibit a threedimensional appearance or woven texture. In addition, the compositionand thickness of the coating layers can be selected to achieve desiredlight reflection and absorption characteristics in order to produce anattractive ornamental appearance.

Referring now to FIGS. 4 and 5, a fixture 34 is shown for holding thebrake disk substrates 26 during coating. Although not visible in FIGS. 4and 5, the working surfaces of substrates 26 a to 26 e have pluralraised projections or island formations as described above in connectionwith FIG. 9. Although the fixture 34 is shown holding five brake disksubstrates 26 a-e, it is to be appreciated that the fixture 34 is merelyexemplary and that fewer or more brake disk substrates 26 could bepositioned on a fixture 34. As shown, the fixture 34 includes threeparallel poles 36, 38, 40 that are mounted on and extend from a baseplate 42. Although the fixture 34 only shows three parallel poles 36,38, 40 it is appreciated that this configuration is only exemplary andthat fewer or more parallel poles could be positioned on the fixture 34.The parallel poles 36, 38, 40 are arranged on the base plate 42 witheach pole 36, 38, 40 spaced at an equal distance from the other twopoles 36, 38, 40. With this cooperation of structure, a plurality ofbrake disk substrates 26 can be stacked on each pole 36, 38, 40. Forexample, as shown, brake disk substrates 26 a and 26 d are stacked onpole 36, brake disk substrate 26 c is stacked pole 38 and brake disksubstrates 26 b and 26 e are stacked on pole 40.

As illustrated in FIGS. 4 and 5, spacers 44 a-e are used to selectivelyseparate adjacent brake disk substrates 26 on each pole 36, 38, 40. Forthe implementation shown, each spacer 44 a-e includes a tube 46 andflange 48 allowing each spacer 44 a-e to be slid over a respective pole36, 38, 40 and positioned as desired. In the implementation shown inFIGS. 4 and 5, the spacing between poles 36, 38 is established to allowthe brake disk substrates 26 on one pole 36, 38, 40 to overlap the brakedisk substrates 26 on an adjacent pole 36, 38, 40. Also for theimplementation shown in FIGS. 4 and 5, the spacers 44 a-e have beensized to prevent brake disk substrates 26 on one pole 36, 38, 40 fromcontacting the brake disk substrates 26 on an adjacent pole 36, 38, 40.

FIGS. 6 and 7 depict a deposition apparatus 50 for coating the brakedisk substrates 26, although other operable deposition apparatus may beused. The deposition apparatus 50 includes a chamber 52 having a body 54and a door 56 that may be opened for access to the interior of thechamber 52 and which is hermetically sealed to the body 54 when thechamber 52 is in operation. The interior of the chamber 52 iscontrollably evacuated by a vacuum pump 58 pumping through a gate valve60. The vacuum pump 58 includes a mechanical pump and a diffusion pumpoperating together in the usual manner. The interior of the chamber 52may be controllably backfilled to a partial pressure of a selected gasfrom a gas source 62 through a backfill valve 64. The gas source 62typically includes several separately operable gas sources. The gassource 62 usually includes a source 62 a of an inert gas such as argonand a source 62 b of Nitrogen gas, each providing gas selectively andindependently through a respective selector valve 65 a or 65 b. Othertypes of gas can also be provided as desired, such as gases required toproduce borides, oxides and/or carbides.

The pressure within the chamber 52 is monitored by a vacuum gage 66,whose output signal is provided to a pressure controller 68. Thepressure controller 68 controls the settings of the gate valve 60 andthe backfill valve 64 (and, optionally, the selector valves 65),achieving a balance of pumping and backfill gas flow that produces adesired pressure in the chamber 52 and thence pressure reading in thevacuum gauge 66. Thus, the gaseous backfilled atmosphere within thechamber 52 is a flowing or dynamic atmosphere.

In the illustrated embodiment, four linear deposition sources 70 aremounted within the interior of the chamber 52 in a circumferentiallyspaced-apart manner. In alternative embodiments, a greater or lessernumber of linear deposition sources may be used, with two or moredeposition sources being used in each embodiment. In FIG. 6, the fourdeposition sources are identified as distinct sources 70 a, 70 b, 70 c,and 70 d, as addressed individually in the subsequent discussion. Thefour deposition sources 70 are generally rectangular bodies having agreatest rectilinear dimension elongated parallel to a source axis 72.This type of deposition source is distinct from either a stationarypoint source or a point source that moves along the length of thesubstrate 26 during deposition procedures.

A support 74 is positioned in the chamber 52. The support 74 produces acompound rotational movement of a fixture 34 mounted thereon. In theillustrated embodiment, the support 74 includes a rotational carriage 76that rotates about an axis 78, driven by a rotational drive motor 80below the rotational carriage 76. Mounted on the rotational carriage 76are six planetary carriages 82. In alternative embodiments, a greater orlesser number of planetary carriages may be used, such as one or more.The planetary carriages 82 are rotationally driven about a rotationalaxis 84 by a planetary drive motor 86 below the planetary carriages 82(see FIG. 7). The speeds of the rotational drive motor 80 and theplanetary drive motor 86 are controlled by a rotation controller 88. Inone embodiment, the rotation controller 88 rotates the rotationalcarriage 76 at a rate of about 1 revolution per minute (rpm).

Continuing with FIGS. 6 and 7, for deposition processing of brake disksubstrates 26, a fixture 34 as described above can be mounted on theplanetary carriage 82, as shown. For commercial operations, a fixture 34having a plurality of brake disk substrates 26 is mounted on eachplanetary carriage 82 in the manner described, as illustrated for one ofthe planetary carriages 82 in FIG. 7.

The temperature in the chamber 52 during deposition is controlled usinga heater 92 that extends parallel to the deposition sources 70 on oneside of the interior of the chamber 52. The heater 92 in one embodimentis a radiant heater operating with electrical resistance elements. Thetemperature of the heating array is monitored by a temperature sensor 94such as an infrared sensor that views the interior of the chamber 52.The temperature measured by the sensor 94 is provided to a temperaturecontrol circuit 96 that provides the power output to the heater 92.Acting in this feedback manner, the temperature controller 96 allows thetemperature of the heating array to be set. In the preferred processing,the heating array is heated to a temperature of from about 1000° F. toabout 1700° F.

FIG. 8 illustrates a cathodic arc source 100 used in one embodiment ofthe deposition source 70. The cathodic arc source 100 includes achannel-shaped body 102 and a deposition target 104. The depositiontarget 104 is in the form of a plate that is hermetically sealed to thebody 102 using an O-ring 106, forming a water-tight and gas-tight hollowinterior 108. The interior 108 is cooled with cooling water flowingthrough a water inlet 110 and a water outlet 112. Two spirally shaped(only sections of the spirals are seen in FIG. 8) permanent magnets 114extend parallel to the source axis 72. Positioned above the depositiontarget 104 exterior to the body 102 is a striker electrode 118. Avoltage VARC is applied between the striker electrode 118 and thedeposition target 104 by an arc source power supply 120. In oneembodiment, VARC is in the range from about 10 to about 50 volts.

The metallic material that forms the deposition target 104 is depositedonto the brake disk substrate 26 together with, if desired, gas atomsproducing gaseous species from the atmosphere of the chamber 52. For theembodiment describe herein, the deposition target 104 is made ofTitanium (Ti) metal.

To accomplish the deposition, an arc is struck between the strikerelectrode 118 and the deposition target 104, locally heating thedeposition target 104 and causing Titanium atoms and/or ions to beejected from the deposition target 104. (The deposition target 104 istherefore gradually thinned as the deposition proceeds.) The strikingpoint of the arc on the deposition target 104 moves in a racetrackcourse along the length of the deposition target 104. A negative biasvoltage VBIAS is applied between the deposition target 104 and brakedisk substrate 26 by a bias power supply 122, so that any positivelycharged ions are accelerated toward the brake disk substrate 26.

In one embodiment, VBIAS is in the range from about −30 to about −600volts. The value selected for VBIAS determines the energy of ionicimpact against the surface of the substrates, a phenomenon termed ionpeening. In one case, VBIAS is initially selected to be a relativelylarge negative voltage to achieve good adherence of the metallic firstlayer 28 (see FIG. 3A) to the brake disk substrate 26. VBIAS issubsequently reduced (made less negative) when the overlying hard layeris deposited, to achieve a uniform, fine microstructure in the overlyinglayer. The values of VBIAS are desirably maintained as low as possible,consistent with obtaining an adherent coating 24. VBIAS is more positivethan −600 volts, and in one embodiment is more positive than −400 volts.If VBIAS is too negative, corona effects and backsputtering may occur atsome regions of the brake disk substrate 26. Thus, while higher VBIASvoltages may be used in some instances, generally it is preferred thatVBIAS be more positive than −600 volts. The cathodic arc source 100 ispreferred, but other types of sources, such as sputtering sources, mayalso be used.

The cooperative selection of the material of the deposition target 104and the gases introduced into the deposition chamber 52 from the gassource 62 allows a variety of coatings 24 to be deposited onto the brakedisk substrate 26, within the constraints discussed previously. Thetotal thickness of the coating 24 in one embodiment is in the range fromabout 1 to about 10 micrometers. If the coating thickness is less thanabout 1 micrometer, the physical properties of the coating 24 areinsufficient to produce the desired results. If the coating thickness ismore than about 10 micrometers, the coating 24 has a high internalstress that leads to a tendency for the coating 24 to crack and spallaway from the brake disk substrate 26 during deposition or duringservice.

These general principles are applied in preparing the coatings 24 ofinterest, as described previously in relation to FIG. 3A. The coating 24of FIG. 3A includes an amorphous metallic first layer 28, such asamorphous metallic Titanium, that contacts and overlays the surface ofthe brake disk substrate 26. The amorphous metallic first layer 28 isdeposited by backfilling the deposition chamber 52 with a small partialpressure of about 5 microns of an inert gas, such as flowing argon(flowing at a rate of about 200-450 standard cubic centimeters perminute (sccm) in the apparatus used by the inventors), and thendepositing metal, such as Titanium, from the deposition target 104 withVBIAS about −400 volts. Because the argon does not chemically react withthe metal, an amorphous metallic first layer 28 is deposited.

As shown in FIG. 3A, a second layer 30, which for the embodimentdescribed herein is a metal Nitride, overlies the amorphous metallicfirst layer 28. The second layer 30 is deposited by backfilling thedeposition chamber 52 with a small partial pressure of about 5 micronsof flowing Nitrogen (flowing at a rate of about 150-500 standard cubiccentimeters per minute in one embodiment), and then depositing metal,such as Titanium, from the deposition target 104 with VBIAS about −50volts. The metal combines with the Nitrogen to produce the metal Nitridein the second layer 30.

The island formations or raised land portions on the brake disksdescribed above facilitate cooling of the brake disk by increasing anddirecting air flow around and between the island formations duringbraking. By increasing the ability of the brake disk to dissipate heat,the risk of brake fade, wear and warpage is reduced, and may potentiallyincrease the effective service life of the brake disk. In addition, thevoids or channels between adjacent island formations reduce the overallweight of the brake disk, reducing the amount of material required.Finally, the island formations can be designed to produce a visuallyattractive appearance in the visible portion of the brake disk, addingto the overall look of a vehicle such as a motor cycle where the brakedisks are clearly visible.

Although the embodiments described above are in the form of brake discs,in other embodiments the island formations could alternatively beapplied to working surfaces of other brake components for frictionalengagement with a braking member, such as the surface of a brake drumwhich is engaged by a brake shoe in a drum brake arrangement.

The above description of the disclosed embodiments is provided to enableany person skilled in the art to make or use the invention. Variousmodifications to these embodiments will be readily apparent to thoseskilled in the art, and the generic principles described herein can beapplied to other embodiments without departing from the spirit or scopeof the invention. Thus, it is to be understood that the description anddrawings presented herein represent a presently preferred embodiment ofthe invention and are therefore representative of the subject matterwhich is broadly contemplated by the present invention. It is furtherunderstood that the scope of the present invention fully encompassesother embodiments that may become obvious to those skilled in the artand that the scope of the present invention is accordingly limited bynothing other than the appended claims.

The invention claimed is:
 1. A method of forming a braking surface on asubstrate material, comprising: machining the braking surface on thesubstrate material to form a plurality of spaced, raised islandformations with channels extending between the island formations;finishing outer surfaces of the plurality of spaced, raised islandformations to form a friction surface, the friction surface configuredto engage a brake pad; and applying a wear and corrosion resistantcoating to the friction surface, the wear and corrosion resistantcoating comprising: a first coating layer of a first coating material,the first coating material comprising a crystalline material; and asecond coating layer of a second coating material; wherein the wear andcorrosion resistant coating is configured to reduce, during use of thebraking surface in braking of a vehicle, wear of the plurality ofspaced, raised island formations relative to the substrate material inan uncoated state.
 2. The method of claim 1, wherein the channelscomprise a roughened base surface.
 3. The method of claim 2, wherein theroughened base surface creates turbulence in air flowing along thechannels in a direction parallel to the outer surfaces.
 4. The method ofclaim 1, wherein the first coating material comprises a metal.
 5. Themethod of claim 4, wherein the second coating layer comprises at leastone compound of the same metal as the first coating layer.
 6. The methodof claim 4, wherein the metal of the first coating layer is selectedfrom a group of metals consisting of titanium, chromium, zirconium,boron, hafnium and alloys thereof.
 7. The method of claim 6, wherein thesecond coating layer comprises a nitride, boride, carbide or oxide ofthe metal used in the first coating layer.
 8. The method of claim 1,wherein the plurality of spaced, raised island formations are formed ofthe substrate material.
 9. The method of claim 1, wherein the finishingcomprises: applying the first coating material to at least the outersurfaces through vapor deposition; and applying the second coatingmaterial over the first coating material through vapor deposition. 10.The method of claim 1, wherein the finishing comprises applying thefirst coating material and the second coating material over an entirearea of the braking surface.
 11. The method of claim 1, wherein thefinishing comprises applying a three-dimensional surface texture to atleast the plurality of spaced, raised island formations.
 12. The methodof claim 11, wherein the three-dimensional surface texture is appliedover an entire area of the braking surface.
 13. The method of claim 11,wherein the three-dimensional surface texture comprises peaks, valleys,and angular surfaces formed between the peaks and the valleys.
 14. Themethod of claim 11, wherein the three-dimensional surface texture isapplied using one or more of bead blasting, sanding, grinding, acidetching, photo-resist etching, roll forming, embossing, stamping,honing, lapping, polishing, blanching, milling, and profiling.
 15. Themethod of claim 11, wherein the finishing further comprises: applyingthe first coating layer to at least the plurality of spaced, raisedisland formations after the three-dimensional surface texture isapplied, the first coating layer being applied through vapor deposition,wherein the first coating layer is deposited onto the braking surface byenergizing a first material source to cause charged particles of thefirst material source to be dissociated from the first material sourceand deposited on at least the plurality of spaced, raised islandformations; and applying the second coating layer to the first coatinglayer through vapor deposition, wherein the second material of thesecond coating layer forms a compound, wherein the second coating layeris deposited by energizing a second material source to cause chargedparticles of the second material source to be dissociated from thesecond material source, introducing a reactive gas which reacts with thecharged particles of the second material that is deposited on at leastthe plurality of spaced, raised island formations; wherein thecombination of the finishing and the vapor deposition causes at leastthe plurality of spaced, raised island formations to exhibit a selectedthree-dimensional surface texture.
 16. The method of claim 1, furthercomprising roughening a base surface of each channel to produce bumps.17. The method of claim 1, wherein the braking surface comprises acentral opening, and a series of radially extending rows of islandformations extending from the central opening to an outer periphery ofthe braking surface.
 18. The method of claim 17, wherein the channelscomprise: radially extending spaces between the adjacent rows of islandformations; and radially spaced gaps between adjacent island formationsin each row.
 19. The method of claim 1, wherein the second coatingmaterial is selected from a group of coating materials consisting ofmetal nitride, metal oxide, metal boride, and metal carbide.
 20. Abraking surface formed on a substrate material by a process comprising:machining the braking surface on the substrate material to form aplurality of spaced, raised island formations with channels extendingbetween the island formations; finishing outer surfaces of the pluralityof spaced, raised island formations to form a friction surface, thefriction surface configured to engage a brake pad; and applying a wearand corrosion resistant coating to the friction surface, the wear andcorrosion resistant coating comprising: a first coating layer of a firstcoating material, the first coating material comprising a crystallinematerial; and a second coating layer of a second coating material;wherein the wear and corrosion resistant coating is configured toreduce, during use of the braking surface in braking of a vehicle, wearof the plurality of spaced, raised island formations relative to thesubstrate material in an uncoated state.